[mkgmap-dev] Questions regarding routing

Fri Jun 7 21:59:53 BST 2013

Hi Carlos,

Carlos Dávila-2 wrote
> El 07/06/13 21:45, GerdP escribió:
>>
>> Questions:
>> 1) If a road with road_speed=4 has e.g. 10 points (= OSM nodes) , and the
>> 3rd point has tag
>> mkgmap:road-speed=-1 and the 8th point has tag mkgmap:road-speed=+1,
>> what is the expected result?
>> I would assume that the road is split into 3 parts, one containining
>> points
>> 1-3,
>> one the points 3-8, and the last one the points 8-10.
>> The 1st part would use the unchanged road_speed value 4, the 2nd part the
>> the value 3 and the last part the value 5.
>> (if this doesn't introduce any short arcs, else splitting makes no sense
>> for
>> these tags)
>> Correct?
> If I recall correctly, if a node is tagged with mkgmap:road-speed it 
> affects the portion of the way from the node before to the tagged one to 
> the node after it, so the above example will result in section 1-2: 
> road-speed=4, section 2-4 r-s=3, section 4-7 r-s=4, section 7-9 r-s=5 
> and section 9-10 r-s=4

yes, I think that is what happens. I just don't understand why it is coded
like that.
The default style doesn't use this feature, so I don't know how it is used.
My thought was that a OSM node has some kind of speed limit tag and that is
translated 
into a mkgmap:road-speed tag. If that is correct, I would assume that the
speed limit
is true as long as no new node with another one is found. Of course this
assumes that
all different speed limit signs are points with the corresponding tags.

Gerd
Gerd

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